Effect of temperature and fertilizer nitrogen on apex development in spring wheat triticum aestivum
Frank, A.B.; Bauer, A.
Agronomy Journal 74(3): 504-509
ISSN/ISBN: 0002-1962 Accession: 005274635
Development of crop growth simulation models has indicated a lack of information on effects of specific environmental factors on growth and yield of hard red spring wheat, T. aestivum L. em Thell. One environmentally sensitive yield component is the number of kernels per ear. The effect of temperature and fertilizer N on early plant growth, apex development and number of spikelets and kernels per ear were studied. [Cultivar] Sinton spring wheat was grown in a controlled environment chamber at 10.degree., 18.degree. and 26.degree. C with 0, 78 and 224 kg N/ha. Irradiance was 1000 .mu.E[einsteins]m-2s-1 and 16-h photoperiod. Duration of the vegetative phase of the apexes was determined for the main stem (M) and the 1st (T1), 2nd (T2) and 3rd (T3) tillers and duration of the spikelet development phase was measured for M. Tillers and leaves were tagged as they appeared and their development related to apex development. Spikelets and kernels per ear were determined for each stem at maturity. Duration of M apex vegetative phase was influenced by temperature but not by N level; the spikelet development phase was influenced by temperature and N level. Duration of the vegetative phase was 24, 22 and 17 days at 10.degree., 18.degree. and 26.degree. C, respectively. Duration of the spikelet development phase was significantly shorter at 26.degree. C (4.8 days) than at 10.degree. C (6.5 days) and 18.degree. C (7.4 days). Development of tiller apexes appeared to be strongly synchronized to development of the M apex. Inflorescence initiation on M occurred at the 5.1 leaf stage at 18.degree. C and at 4.4 leaf stage for the 10.degree. and 26.degree. C treatment. Kernels per ear for the main stem and tillers decreased significantly from 27.2 and 24.8, to 18.5 as temperature increased from 10.degree. to 18.degree. to 26.degree. C, respectively. Fertilizer N levels of 0, 78 and 224 kg N/ha produced kernel numbers of 20.8, 23.5 and 26.2, respectively. Tillers originating at the coleoptile node produced fewer kernels per ear at 10.degree. C than leaf tillers, but not at 18.degree. or 26.degree. C. The percentage of 1st tillers elongating from the coleoptile node was 62, 47, and 30 at 10.degree., 18.degree. and 26.degree. C, respectively. Early vegetative growth and apex development is more sensitive to temperature than to N fertilization. Kernels per ear for tillers is controlled in part by their synchronization to the development of the M apex.